Scuzzle, So I could assign pins 1-64 to the Great keyboard, 65-128 to the Swell keyboard on core no. 1, assigning the channel number "1" to the first 64 , and "2" to the second 64. I would then have to add a second core for the pedal board which only has 32 pedals, plus 10-20 stop switches (on-off switches). All this with the midiio128 core. On the output side. eventually I will add actual pipes to the organ which would be in ranks of 64. at this point possibly 5 ranks. Could I daisey chain digital outs to the midiio128 or would I have to add additional cores to cover the 5X64 pipes? Operating actual pipes, the PC won't be in the picture which brings up more questions. In terms of hardwire, the organ console stop switches enables the particular rank or 64 pipes. Performing the logic with midi, would mean the a stop input would enable a bank of 64 outputs being keyed from one of the keyboards or pedalboard. How could that be done with the midi cores. I know that I could do it with relays, but would rather do it with progamming. There are several other features to explore. Thorsten mentioned transposition, but also: couplings. There are pipe ranks that play only from the swell keyboard, same for the Great and the pedal. the couplers allow you to couple ranks swell to great, great to swell, great to pedal, pedal to great, pedal to swell. There is more, but we can save them for later. I understand how the .ini file for the midi128 is customized and downloaded from the pc to the core memory. what is the operating system for the PIC itself? How do you load the basic operating system into the PIC? Thanks for all the info. Thorsten, I would appreciate communicating with anyone interested in going down the conversion path. There are numerous things to deal with, and having some brainstorming time would be great. Thanks,